Blowout prevention apparatus

ABSTRACT

Apparatus comprising a failsafe series of shutoff valves therefore situated below the mudline of a completed well such that a rapid removal or damage of a wellhead assembly will not create a catastrophe as the well may be controlled at a point below the mud line.

United States Patent [1 1 Priebe et al. 1 July 10, 1973 [54] BLOWOUT PREVENTION APPARATUS 3,481,395 12/1969 Sizer et al. 166/5 [7 Frank Robert nibble; 3333'322 151321 $2521.11:31:11...........:::::::::::::::' 6783 Frank T. Jones, all of Houston, Tex.

[73] Assignee: Cities Service Oil Company, Tulsa, primary Examiner Marvin Champion Okla- Assistant Examiner-R0bert A. Hafer [22] Filed; 14 1970 Attorney-J. Richard Geaman [21] Appl. No.: 97,760

' [57] ABSTRACT 2 5" Apparatus comprising a failsafe series of shutoff valves d l 5 6 88 89 therefore situated below the mudline of a completed 1 o arc well such that a rapid removal or damage of a wellhead assembly will not create a catastrophe as the well may [56] uNl g gf fzifg ggi s be controlled at a point below the mud line.

3,209,829 10/1965 Haeber 166/.6 7 Claims, 1 Drawing Figure 1 BLOWOUT PREVENTION APPARATUS BACKGROUND OF THE INVENTION The present invention relates to apparatus for the completionof production wellbores. Moreparticularly, the apparatus of the present invention is a failsafe mechanism by which blowouts may be prevented in completedhwells.

The recent influx in deep hole drilling has created a problernwhich heretofore has not been realizedwithin the drilling engineering field. It has been found that when deepwells are completed inhigh pressure resen voirs, extreme precautions must be taken to prevent blowouts in production strings. Thiseffect has been paramounted by the combination of increasedoffshore drilling andlthe severe weatherconditions which may atany moment remove the wellhead from a production string. The possibilities .ofwellheadyfailure require the development of a failsafe mechanism. by which a well may be shut in downhole at any. time.

Recent catastrophes causing extensive fires and oil spillage due, to offshore drilling rig blowouts have brought to afocal point the requirements for afailsafe device in addition tostorm chokes, for therefor shutting in of .a. completedwell when achristmastree is:

damaged or removed.from thetwellhead. What isrequired is apparatus.and atechnique whichprovidesa failsafe mechanismforthe prevention of offshore blowouts in completed wwells. so to curtail the; therefor numberof these disasters.

It is an object.ofthepresentinvention to providean apparatus t'orl the prevention of offshore, blowouts in completed wells. It. is another object vofthe present invention to provide a, system ofshutoff valves placed within thelcompletedwells such that a rapid removal or damage of the christmas tree assembly, at the, wellhead will not cause a catastrophe It is still a furtherobjectofthepresentinvention to provide a failsafe series .of shutoff ,valves within acompleted well so thifizSI'lOllId ablowoutwbeimminent, the

well may be controlled at a point below the mudline through the series of failsafeshutoff valves.

With theseand other objects in mind, the, presentinvention will bemore fullydisclosed through particular.

reference to the, followingdrawingand description;

SUMMARY OF THE INVENTION nected in line with each of; the; production tubing.

strings. Means for isolating and releasingthe portions of the production, tubingstring below the. failsafe shutoff valves fromthe annulusformed betweenthe production tubing string and easing strings are, provided. A

relief tubingstringis connected to the annulusformed between the; production tubingtstrings and positioned casing string andtraverses to the surface within the annulus formed between thepositioned casing string and. the cased wellboreof the wells A failsafe release valve.

is connected inline withthe relief tubing stringnear the connectionof. the relief tubing string to. the positioned casingstringtso as to provide ameans for relieving the pressure formed in the annulus between the positioned casing string and the production tubing strings should such pressure buildup be incurred.

Generally, in the blowout preventer assembly of the present invention, the means for isolating and releasing the portion of the production tubing strings below the failsafe shutoff valve comprise a tubing bowl catcher positioned below the failsafe shutofi valves and the po sitioned casing string. A tubing hanger is positioned within the tubing bowl catcher so as to receive each production tubing string from its respective producing horizon and a similar production tubing string from the wellhead. The apparatus further includes means for releasing the producing production tubing string below the tubing hanger so that any fluidcontained in the pro duction string may bereleased into the annulus formed between the production tubing string and the positionedcasing string so that it may be produced through the relief tubing string to the surface.

In the use of the blowout preventer assembly of the present invention as a blowout preventer assembly for anoffshore oilrig, the blowout preventer shouldbe po-. sitioned below the mudline in the wellbore such that any catastrophe onthe oil rig will not affect the failsafe mechanism of the blowout preventer assembly described herein.

BRIEF DESCRIPTION OF THE DRAWING The particular aspectsof the present invention may be more fully understood by referral to theaccompanying FIGURE in which one embodiment of a failsafe blowout preventer assembly is depicted for use in a completed production well.

DETAILED DESCRIPTION OF THE INVENTION The blowout preventer assembly of the present invention comprises a failsafe series of shutoff valves placed below the mudline in acompleted wellof an offshore productionplatform or below the wellhead assembly inian onshore well such that the rapid removal or damage to a christmas tree or wellhead assembly. of the well will not cause a catastrophe. Therefore, through the use of the blowout preventer assembly of the present invention, thewell may becontrolledat a point below the wellhead assembly, where control is normally issued, so that major catastrophies or blowouts may be prevented.

A preferred embodiment of the present invention is depicted in the accompanying FIGURE in which awell has been drilled and completed with cemented exterior casing string 101 withvarious inner casing strings 104 being turned down the hole, exposing casing joint connectors 117'. Exterior casing string 101 contains a run repair. Therelieftubing string l05may notbe installed until required as the failsafe relief valve 106 is readily accessible for quick connections. The tieback tubing string 102 contains one or more production tubing strings 118.

The production tubing strings 118 are run and spaced out in a tubing hanger 109. A tubing connector 108 connects the production tubing string 118 within the tubing hanger 109 to a short length of tubing 115 to a failsafe shutoff valve 114. The tubing hanger 109 is then landed in the tubing bowl catcher 103. The tubing hanger 109 will be secured in the tubing bowl catcher 103 by spring loaded sheer pin 110 and pressure deforming ring 111 secured by set screw 112. The short length of tubing 1 is run to the tubing hanger 109 and landed in the tubing connector 108. A snap ring (not shown) may be required to secure the tubing connector 108 in the tubing hanger 109. For release and repair operations, a J-slide, or similar locking means, may be utilized within pressure limitations between failsafe shutoff valve 114 and the short production tubing string 115 to facilitate pulling this portion of the upper production tubing string 116 and failsafe shutofi' valve 114.

Upon the cellar deck of the production platform, a simple plate will cover the annulus between the exterior casing string 101 and tieback tubing string 102. Under normal operations, this simple plate need not be pressure tight as it will be pierced to allow the relief tubing string, if installed, to pass to the surface. The failsafe relief valve 106 on the relief tubing string 105 permits normal pressure observations to be taken with failsafe shutoff valves 114 positioned between the short length of tubing 115 and upper production string 116, becoming backup valves for emergency shutin operations. Unless a tubing or tubing hanger leak occurs, there should be no pressure on the relief tubing string 105. A simple single or dual tubing head may be installed on top of the tieback tubing string 102. This head will contain a double master valve on each production tubing string 116, one master valve being automatic and one mechanical. Pressure may be applied to the annulus formed between the casing 101 and tieback tubing string 102, at the surface, to assist the controlling of the tubing hanger 109, keeping it seated and vented if a tubing leak occurs below the blowout preventer assembly.

In conjunction with the blowoutpreventer assembly described, normal means for releasing the production tubing string below the hydraulic set packer may be provided. These releasing means may comprise the mere turning of the production tubing string from within the hydraulic set packer such that the downhole portion of the production tubing string would be disconnected from the hydraulic set packer and therefore allow the fluid contained therein to enter the annulus formed between the casing string and production tubing string such that it may be produced through the relief tubing string. Back pressure may also be applied through the relief tubing string to shut off the failsafe shutoff valves. in conjunction with these releasing means, a slit tubing connector may be utilized to join the production tubing strings held in the tubing hanger so that a simple'turn of the tubing connector will lower the production tubing string below the tubing connector, allow fluid to flow through the slit portion of the tubing connector and into the annulus formed between the production tubing string and the casing string such that quick pressure release is available for the production tubing strings.

The blowout preventer assembly of the present invention may be used onshore at shallow depths below the wellhead assembly of the drilling platform or production unit. Normally, the blowout preventer assembly should be located to 50 to feet below the ground surface. However, in the use of the blowout preventer assembly on offshore drilling rigs or production platforms, the blowout preventer assembly would normally be located from 50 to 100 feet below the mudline of the well such that any catastrophe on the platform itself or on the ocean floor would not interfere with the operation of the blowout preventer assembly. It could be used in conjunction with conventional storm chokes in the well and give a failsafe method of containing any fluids from producing horizons within the wellbore and not allow their escape into the surrounding environment.

The apparatus of the present invention consists of standard completion equipment consisting of failsafe shutoff valves which may be hydraulically operated or electrically operated from the surface or may be operated by pressure surges experienced within the production tubing strings themselves. The downhole tubing bowl catcher and tubing hanger are designed for the particular installation in which they are used but are conventional equipment well known to the oil industry and do not require unconventional design constraints in their construction. Therefore, various and sundry equipment configurations are available for accomplishing the purpose of the present invention and will become apparent to those familiar in the art of blowout prevention equipment. It is also noted that the valve assembly of the present apparatus is an addition to the normal complement of master valves and storm chokes utilized in offshore completions for blowout prevention. The apparatus, therefore, is a failsafe mechanism in addition to the complement of storm chokes and shutoff apparatus normally contained in completed wells.

Recent catastrophies causing extensive damage to offshore drilling rigs through blowouts, even those containing storm chokes in which the storm chokes failed due to damage of the wellbore completion itself, may be curtailed through the utilization of the failsafe blow out prevention assembly described herein. Therefore, through use of the apparatus of the present invention, a failsafe mechanism is derived for the prevention of offshore blowouts in completed wells so that the redundancy of these disasters may be curtailed.

While the present invention has been described herein with respect to particular embodiments thereof, it will be appreciated by those skilled in the art, however, that various changes and modifications may be made without departing from the scope of the invention.

Therefore, we claim:

1. A blowout preventer assembly for use in a cased and completed well having at least one production tubing string, surrounded by at least one casing string, connecting subterranean producing horizons with a wellhead, comprising:

a. a failsafe shutoff valve connected in line with each of the production tubing strings;

b. means for isolating the portions of the production tubing strings below the failsafe shutoff valves from the annulus between the production tubing string and easing string;

c. a relief tubing string connected to the annulus formed between the production tubing string and easing string below the isolation means,

d. a failsafe relief valve connected in line with the relief tubing string near the connection of the relief tubing string with the casing string.

2. The blowout preventer assembly of claim 1 in which the means for isolating the portions of the producing tubing strings below the failsafe shutoff valves comprises:

a. a tubing bowl catcher positioned below the failsafe shutoff valves in the casing string; and

b. a tubing hanger positioned within the tubing bowl catcher so as to receive each production tubing string from the respective producing horizon and the similar production tubing string from the wellhead.

3. The blowout preventer assembly of claim 2 in which the well is offshore and the blowout preventer assembly is located below the mudline in the wellbore.

4. The blowout preventer assembly of claim 2 further comprising:

a. a pressure deformable ring located about the tubing hanger; and

b. a set pin located in the lower portion of the tubing hanger and positioned so as to retain the tubing hanger in the tubing bowl catcher.

5. The blowout preventer assembly of claim 2 further comprising means for releasing the production tubing string below the tubing hanger.

6. The blowout preventer assembly of claim 5 in which the means for releasing the production tubing string below the tubing hanger comprises a slotted tubing connector positioned in the production tubing string within the tubing hanger and the tubing bowl catcher.

7. The blowout preventer of claim 5 in which the relief tubing string traverses to the surface within the annulus formed between the casing string and the cased wellbore of the well. 

1. A blowout preventer assembly for use in a cased and completed well having at least one production tubing string, surrounded by at least one casing string, connecting subterranean producing horizons with a wellhead, comprising: a. a failsafe shutoff valve connected in line with each of the production tubing strings; b. means for isolating the portions of the production tubing strings below the failsafe shutoff valves from the annulus between the production tubing string and casing string; c. a relief tubing string connected to the annulus formed between the production tubing string and casing string below the isolation means, d. a failsafe relief valve connected in line with the relief tubing string near the connection of the relief tubing string with the casing string.
 2. The blowout preventer assembly of claim 1 in which the means for isolating the portions of the producing tubing strings below the failsafe shutoff valves comprises: a. a tubing bowl catcher positioned below the failsafe shutoff valves in the casing string; and b. a tubing hanger positioned within the tubing bowl catcher so as to receive each production tubing string from the respective producing horizon and the similar production tubing string from the wellhead.
 3. The blowout preventer assembly of claim 2 in which the well is offshore and the blowout preventer assembly is located below the mudline in the wellbore.
 4. The blowout preventer assembly of claim 2 further comprising: a. a pressure deformable ring located about the tubing hanger; and b. a set pin located in the lower portion of the tubing hanger and positioned so as to retain the tubing hanger in the tubing bowl catcher.
 5. The blowout preventer assembly of claim 2 further comprising means for releasing the production tubing string below the tubing hanger.
 6. The blowout preventer assembly of claim 5 in which the means for releasing the production tubing string below the tubing hanger comprises a slotted tubing connector positioned in the production tubing string within the tubing hanGer and the tubing bowl catcher.
 7. The blowout preventer of claim 5 in which the relief tubing string traverses to the surface within the annulus formed between the casing string and the cased wellbore of the well. 